The present invention relates generally to rim holding tire changers, and more particularly to the clamps used to hold a wheel in a fixed relation to the table of a rim holding tire changer while a tire is mounted on or removed from the rim.
One rim holding tire changer can be used to mount or dismount the tires for a variety of types of vehicles. It is not uncommon for such a changer to be used to mount and dismount the tires on the rims of automobiles, pick-up trucks, motorcycles, and the like. Further, with some automobile rims, the rims are quite decorative, made of polished chrome and the like and thus require a special clamp in order to avoid marring the surface of the rim.
It will be appreciated by those skilled in the art of designing and manufacturing equipment used to change the tubeless tires mounted on the rims of cars, light trucks and other vehicles, that such equipment must perform quickly and efficiently in order to be competitive in the marketplace. Modest improvements in the industry can thus become significant.
In the normal tire-changing procedure, the operator places a rim on the table of the rim holding tire changer, secures the rim to the table, places a tire over the rim, mounts the tire on the rim by using the mount/dismount head to guide the bead over the rim, and then fills the air chamber of the tire with air to inflate the tire. This procedure is described in detail in U.S. patent application Ser. No. 08/516,129, the substance of which is incorporated here and by reference, and which is assigned to the Assignee of the present invention.
For several years, automatic type tire changers have been in use for the repair and replacement of tires. There have been two basic types of changers in use over the past 15 or 20 years. One type makes use of the center hole of a wheel to secure the wheel during dismounting and mounting of a tire. A tire changer of this type utilizes a threaded shaft and threaded cone device to maintain the position of the wheel during the tire changing process.
A second type of tire changer is known as a rim holding tire changer and is the type of equipment for which Applicant's invention is designed. It utilizes claws to grip the rim of the wheel to stabilize the wheel and maintain the wheel in position on the changer. Examples of the type of equipment involved are the rim holding tire changers manufactured by Hennessy Industries, Inc., Applicant's assignee, and marketed under the trademarks "COATS.RTM." and "AMMCO.RTM." including the COATS.RTM. models 5030A and the model 5060A-E and 5060AX-EX. Other manufacturers of such equipment include FMC Corporation of Chicago, Ill., Corghi of Correggio, Italy and Sice of Correggio, Italy. Equipment of this type has been readily available in the market for many years, is the subject matter of numerous patents and has been described in a variety of publications, bulletins, brochures, operating and instruction manuals, and the like. One such machine is illustrated in the design patent issued to Applicant as co-inventor in Design U.S. Pat. No. 293,916.
A machine of this type generally has a tire changing table surface on which the wheel rests while the tire is mounted or dismounted. The clamp is used to secure the wheel to the table top of the tire changer while the tire is mounted or dismounted. It is critical that the wheel be securely mounted during this process as it requires a considerable amount of force to mount and dismount a tire from the wheel rim. If the wheel is not securely held in place, the person operating the machine and any bystanders could be injured by a wheel jumping off the tire changer. While it is important that the wheel be securely positioned, it is also important to the consumer that this be accomplished in a manner that does not damage the rim.
A clamp for use in such an apparatus is generally constructed from steel or a similar hard metal and formed so that it can be used in two ways, either by clamping the outer periphery of the rim of the wheel or by clamping the wheel from inside the rim. When a wheel is clamped on the outside, there is often some amount of rotational slippage during the procedure which tends to cause damage to the rim and mar its appearance. Clamping the wheel from the inside also has as a drawback potential damage to the wheel rim. Because of the smooth surface of the inside of the wheel rim, a clamp must have a sharp point or serration to grip the wheel sufficiently. This further damages the appearance of the wheel rim.
In an effort to prevent damage to the wheel, manufacturers of tire changers have attempted to design clamps having claws that can provide stability without marring the wheel. One solution for use in situations where the wheel is clamped from the outside of the wheel has been to cover the claw or gripping portion of the clamp with a plastic material. Such a protective covering does prevent the hard surface of the claw from gouging into the wheel, but it does not eliminate damage resulting from rotational slippage.
To prevent damage when clamping the inside of a wheel, manufacturers have commonly provided rubber blocks that are compressed between the claw and the inside of the wheel. However, the rubber blocks cannot effectively secure a rim unless the wheel is clean and free of dirt. If the wheel is not clean, it can slip and jump off the rubber blocks in a dangerous manner.
Another option has been to put nylon booties over the clamp to protect the wheel rim surface. While this does reduce the damage to the wheel, it does not eliminate all damage to the rim surface from the grip of the claw.
What is needed, then, is a clamp having claws configured to maintain a wheel in place on a tire changing apparatus in a manner that is safe for the machine's operator and will not damage the wheel rim or allow the wheel to slip or jump off the machine. Furthermore, such a clamp should be capable of being used as a fixed clamp or an adjustable clamp, to grip the wheel rim from either the inside or the outside and should allow for inexpensive components that can be field repaired by the user.